Concurrent Path Planning for the End Effector and the Mobile Platform of an Autonomous Mobile Manipulator

The autonomous mobile manipulator (AMM) that is able to navigate complicated environments and handle objects plays a crucial role in production lines of unmanned factories and warehouses automation. Path planning is a crucial function for an AMM to perform various tasks in a complicated environment. Efficiency, obstacle avoidance, (nonholonomic) kinematic constraints of AMMs and smoothness of the path are important factors that should be considered in path planning. Moreover, we consider to plan the paths of the manipulator and the mobile platform concurrently such that they can move simultaneously to reduce the execution time of a task. This paper proposes RRT-Connect-based path sampling and midpoint smoothing methods for this purpose. By sampling the paths of the end effector and the mobile platform separately, the path sampling can be accomplished efficiently. Then, the simple and effective midpoint smoothing algorithm is applied to generate a smooth and collision-free path based on the sampled points in the previous step. Simulations are conducted to verify the effectiveness of the proposed method in complicated environments like a warehouse with obstacles.